The use of low levels of visible or near infrared light (LLLT) for reducing pain, inflammation and edema, promoting
healing of wounds, deeper tissues and nerves, and preventing tissue damage by reducing cellular apoptosis has been
known for almost forty years since the invention of lasers. Originally thought to be a peculiar property of laser light
(soft or cold lasers), the subject has now broadened to include photobiomodulation and photobiostimulation using
non-coherent light. Despite many reports of positive findings from experiments conducted in vitro, in animal models
and in randomized controlled clinical trials, LLLT remains controversial. This likely is due to two main reasons;
firstly the biochemical mechanisms underlying the positive effects are incompletely understood, and secondly the
complexity of rationally choosing amongst a large number of illumination parameters such as wavelength, fluence,
power density, pulse structure and treatment timing has led to the publication of a number of negative studies as well
as many positive ones. In recent years major advances have been made in understanding the mechanisms that
operate at the cellular and tissue levels during LLLT. Mitochondria are thought to be the main site for the initial
effects of light and specifically cytochrome c oxidase that has absorption peaks in the red and near infrared regions
of the electromagnetic spectrum matches the action spectra of LLLT effects. The discovery that cells employ nitric
oxide (NO) synthesized in the mitochondria by neuronal nitric oxide synthase, to regulate respiration by competitive
binding to the oxygen binding of cytochrome c oxidase, now suggests how LLLT can affect cell metabolism. If
LLLT photodissociates inhibitory NO from cytochrome c oxidase, this would explain increased ATP production,
modulation of reactive oxygen species, reduction and prevention of apoptosis, stimulation of angiogenesis, increase
of blood flow and induction of transcription factors. In particular, signaling cascades are initiated via cyclic
adenosine monophosphate (cAMP) and nuclear factor kappa B (NF-&kgr;B). These signal transduction pathways in turn
lead to increased cell proliferation and migration (particularly by fibroblasts), modulation in levels of cytokines,
growth factors and inflammatory mediators, and increases in anti-apoptotic proteins. The results of these
biochemical and cellular changes in animals and patients include such benefits as increased healing in chronic
wounds, improvements in sports injuries and carpal tunnel syndrome, pain reduction in arthritis and neuropathies,
and amelioration of damage after heart attacks, stroke, nerve injury and retinal toxicity.

While Low-level Light Therapy (LLLT) has demonstrated efficacy for certain indications, some aspects of the technology are still controversial. Clinical studies on LLLT range from low quality anecdotal studies to blinded, randomized, control clinical studies. These have used a variety of wavelengths, optical powers and variations in other laser parameters. While these studies show a large range in treatment outcome, comparison of treatment efficacy between these studies with respect to light dose is all but impossible since the light dose characterization in the LLLT field has not been properly defined and is not standardized. Surface irradiance is typically used in the LLLT field as the light dose parameter, ignoring factors such as tissue optical properties, beam divergence, pulsing of the source and tissue thickness to the organ or joint of interest. Drawing on experience with light dosimetry for photodynamic and photothermal therapy, we will provide an overview of light transport and dosimetry in tissue and its implications for LLLT dosimetry. In particular, we suggest that the proper measure of dose is the light fluence rate delivered to the organ or tissue of interest, usually several millimeters below the tissue surface. We have developed a technique that provides an estimate of the subsurface fluence rate based on the diffuse reflectance measured at the tissue surface. Using Monte Carlo simulations and measurements on tissue simulating phantoms, we demonstrate that this technique can be used to predict the subsurface fluence rate to within 30% of the actual value at 3-10 mm below the tissue surface.

The effects of phototherapy on herpes lesions have been clinically demonstrated by either preventing the lesion
formation or speeding their repair. The aim of this in vitro study was analyze the effect of phototherapy on epithelial
cells and HSV-1 in culture. Cultures of HSV-1 and epithelial cells (Vero cell line) were used. The irradiations were done
using a GaAlAs laser (660 e 780 nm, 4.0 mm2). One, two and three irradiations with 6 h-intervals were done. The
experimental groups were: Control: non-irradiated; 660 nm and 3 J/cm2 (2.8 sec); 660 nm and 5 J/cm2 (3.8 sec); 780 nm
and 3 J/cm2 (1.9 sec), and 780 nm and 5 J/cm2 (2.5 sec). The HSV-1 cytopatic effect and the cell viability of irradiated
cultures and controls were analyzed in four different conditions: irradiation of non-infected epithelial cells; epithelial
cells irradiated prior infection; virus irradiated prior infection; irradiation of HSV infected cells. The mitochondrial
activity and cytopathic effects were assessed. The number of irradiations influenced the cell growth positively and
proportionally, except for the 660 nm/ 3 J/cm2 group. Any variation in cytopathic effects was observed amongst the
experimental groups. The viability of infected cells prior irradiation was significantly higher than that of non-irradiated
cultures when 2 irradiations were done. Under the experimental conditions of this study we concluded that phototherapy
is capable of enhancing epithelial cell growth and prolonging cell viability of HSV-1 infected cells. Positive benefits of
phototherapy could be resultant from prolongation of infected cells viability, corroborating with host defenses.

Monochromatic light therapy (MLT) is still not a clinical modality due to conflicting and low predictable outcomes. This likely is due to the mismatch between the accuracy of optical dosimetry employing the theoretically predicted or empirically found dosages and the dynamic requirements of photobiostimulation to dosage. The same doses delivered to a target area can be stimulatory or not depending on the dynamic changes of tissue optical parameters in vivo. Since the optical parameters of tissue and, hence, the radiant energy absorbed in the target area change during the treatment, it is important monitoring and coordinating the dosage with these changes.
In this paper we analyze potentials of advancing to dosimetry that meets the dynamic requirements of the MLT to dosage. Both the tissue optical clearing and the feedback control of irradiation are considered. It is pointed out that the key physiological parameter influencing the variability of actual dose is the blood microcirculation. Even the optimal doses of continuous light irradiation may produce negative therapeutic effect at the time when the target tissue is depleted of blood and cannot maintain the energetic requirements of treatment. It is shown that synchronization of irradiation with the patient's pulse and breathing waves excludes cycles of negative responses and individualize the dosage.

Angiogenesis is essential for normal growth, tissue repair and regeneration. Its stimulation accelerates repair and regeneration including wound healing where these processes are delayed. Its inhibition can reduce the rate of growth of solid tumors. Phototherapy can accelerate the resolution of acute inflammation with the result that the proliferative phase of tissue repair, when angiogenesis occurs, begins earlier than in sham-irradiated controls. Evidence that angiogenesis is enhanced in dermal repair, tendon repair and bone regeneration in rodents is presented. The cellular mechanisms that control angiogenesis involve the interaction of endothelial cells, macrophages, pericytes and other cells in response, for example, to changes in the availability of oxygen in the local environment. Pericytes and macrophages modulate endothelial cell proliferation; pericytes guide endothelial cell migration. The stimulation of endothelial cell proliferation in vitro following exposure to red (660 nm) and infrared (820 nm) radiation, 15 mW, at 2-8 J/cm2 is presented. 1J/cm2 was ineffective. 820 nm irradiation, 15 mW, at 8 J/cm2 was observed to inhibit pericyte proliferation in vitro. Indirect effects on endothelial cell and pericyte proliferation followed stimulation of soluble mediator production by macrophages following exposure to red and infrared radiation. The potential clinical significance of the results obtained is discussed and the necessity of clinical trials emphasized.

In this study, a preliminary approach for pain relief using a novel pulsated LED device
was conducted. 12 patients were treated with a Photopuncture device designed by
SORISA, which consisted in a 10-channel LED system at 617 nm. 15 patients with
different pain localizations were treated: cervicobrachialgia (3 cases), lumbago / sciatica
(4 cases), gonalgia (3 cases), cephalalgia (2 cases), talalgia (1 case), epicondylitis (1
case) and trigeminal neuralgia (1 case). To characterize the pain level, the Categorical
Pain Scale (none (0), mild (1-3), moderate (4-6) and severe (7-10)) was used. Just
patients with severe pain (7-10) were treated. Patients were treated twice a week for 25
minutes; 5 to 8 sessions were given at the following treatment parameters: 10 mW per
channel pulsed at 60 Hz with a 50 % duty cycle. The total dose for point was 7.5 J. To
characterize the response to the treatment, the results were classified as: "no result", no
changes in pain degree; "poor", pain decreased one category; "good", pain decreased
two categories; "very good", complete healing (no pain). The results were: 1 case with
"very good" result; 11 cases with "good" result; 3 cases with "poor" result; and 0 cases with "no result". We conclude that the Photopuncture led device may be a good
alternative to classical Acupuncture in pain relief, although further experimentation is
required.

This study investigates whether low level light treatment (LLLT) can enhance the expression of Peripheral-type
mitochondrial benzodiazepine receptors (PBRs) on the glioma-derived tumour cell line, CNS-1, and
by doing so promote the synthesis of protoporphyrin IX (PpIX) and increase the photodynamic therapy
(PDT)-induced cell kill using 5-aminolevulinic acid (ALA). The endogenous photosensitizer, (PpIX) and
related metabolites including coproporphyrin III are known to traffic via the PBRs on the outer
mitochondrial membrane on their passage into or out of the mitochondria. Astrocyte-derived cells within
the brain express PBRs, while neurons express the central-type of benzodiazepine receptor. CNS-1 cells
were exposed to a range of differing low-level light protocols immediately prior to PDT. LLLT involved
using broad-spectrum light or monochromatic laser light specific to 635 or 905 nm wavelength. Cells
(5&mgr;105) were exposed to a range of LLLT doses (0, 1 or 5 J/cm2) using a fixed intensity of 10 mW/cm2 and
subsequently harvested for cell viability, immunofluorescence or western blot analysis of PBR expression.
The amount of PpIX within the cells was determined using chemical extraction techniques. Results confirm
the induction of PBR following LLLT is dependent on the dose and wavelength of light used. Broadspectrum
light provided the greatest cell kill following PDT, although LLLT with 635 nm or 905 nm also
increased cell kill as compared to PDT alone. All LLLT regimens increased PBR expression compared to
controls with corresponding increases in PpIX production. These data suggest that by selectively increasing
PBR expression in tumour cells, LLLT may facilitate enhanced cell kill using ALA-PDT without damaging
surrounding normal brain.

Over the past few decades, many efforts were devoted to study low power laser and cellular interaction. Some of the
investigations were performed on cell populations. In this work fiber-optic based nano-probe is used for the precise
delivery of laser light on to a single cell and the mechanism of light interaction with the cell during irradiation was
studied. A human skin fibroblast cell line was utilized in this investigation. The human fibroblasts were irradiated under
two different schemes of exposure: (1) entire cell population was irradiated within a Petri dish using a fan beam, (2)
laser energy was precisely delivered on to a single cell using fiber-optic nano-probe. Studies were conducted by
variation of laser intensity, exposure time, and the energy dose of exposure. Proliferative effect of laser irradiation was
determined through cell counting for both exposure schemes. Enhancement of the rate of proliferation was observed to
be dependent on laser parameters and method of laser delivery. Variation of total energy dose had greater effect on the
enhancement of the rate of cellular proliferation compared to that of laser intensity. The photobiostimulative effect was
also observed to have a finite life-time. Fluorescent life-time imaging of reactive oxygen species (ROS) was performed
during the single cell exposure method. ROS generation was found to depend strongly on both laser energy doses and
irradiation time. It is demonstrated in this communication that by using specially engineered nano-probes, laser light can
be precisely delivered on to a targeted single cell.

The role of low light intensity in suppressing metabolic activity of transformed
cell lines was investigated through the applications of a 1,552nm wavelength pulsed
picosecond laser. Human malignant glioblastoma, human leukemia HL-60, and the NIH
3T3 cell lines were used. The cells were grown in 96 well plates and exposed in their
respective growth culture media with 10% (v/v) fetal bovine serum under various fluence
exposure conditions ranging from 0.115 - 100 J/cm2. All cell lines were exposed at a
constant average intensity value of 0.115 W/cm2; 25 kHz repetition rate with 1.6 micro-joule
per pulse; pulse duration = 2.93 picosecond. The human malignant glioblastoma
and the HL-60 cell lines exhibited a monotonic decline in metabolic activity (down 50 - 60%) relative to their respective sham exposed control counterparts between the fluence
values of 0.115 J/cm2 to 10 J/cm2. The NIH 3T3 cells exhibited a maximum suppression
of metabolic activity at the fluence value of 50 J/cm2. Metabolic activity was measured
through the colorimetric MTS metabolic assay. Interestingly, for all cell lines the
metabolic activity was found to return back to the sham exposed control levels as the
fluence of exposure was increased up to 100J/cm2.

It has been known for many years that low level laser (or light) therapy (LLLT) can ameliorate the pain, swelling
and inflammation associated with various forms of arthritis. Light is absorbed by mitochondrial chromophores
leading to an increase in ATP, reactive oxygen species and/or cyclic AMP production and consequent gene
transcription via activation of transcription factors. However, despite many reports about the positive effects of
LLLT in medicine, its use remains controversial. Our laboratory has developed animal models designed to
objectively quantify response to LLLT and compare different light delivery regimens. In the arthritis model we
inject zymosan into rat knee joints to induce inflammatory arthritis. We have compared illumination regimens
consisting of a high and low fluence (3 J/cm2 and 30 J/cm2), delivered at a high and low irradiance (5 mW/cm2 and 50 mW/cm2) using 810-nm laser light daily for 5 days, with the effect of conventional corticosteroid
(dexamethasone) therapy. Results indicated that illumination with 810-nm laser is highly effective (almost as good
as dexamethasone) at reducing swelling and that longer illumination time was more important in determining
effectiveness than either total fluence delivered or irradiance. Experiments carried out using 810-nm LLLT on
excisional wound healing in mice also confirmed the importance of longer illumination times. These data will be of
value in designing clinical trials of LLLT.

The aim of this study was to analyze the effects of phototherapy with low intensity laser on the inflammatory reaction after rat brain injury. Cryogenic injury was performed at the brain of 16 male Wistar rats (250-300g) using a cooper probe at -80º C. Immediately, 24 h and 48 h later, the rats received laser irradiation using a GaAlAs laser (830 nm, 100 mW). The samples were randomly divided into four groups (n= 4 per group): A: control (non- irradiated); B: energy density of 14.28 J/cm2; C: 28.57 J/cm2; D: 42.85 J/cm2. Three days later, the cerebral vascular permeability and the inflammatory cells at the trauma site were evaluated. For vascular permeability analysis, 2 h prior sacrifice an intra vascular injection of Evans blue stain was done in the rats. For inflammatory cells counting, frozen samples were sectioned and the histological slides were stained with Giemsa. The data were compared by either ANOVA or Kruskall-Wallis complemented by the Dunn's test. The irradiated groups presented higher cerebral vascular permeability than controls (A: 2.6 ± 0.8; B:12.0 ± 2.0; C: 13.1 ± 4.1, and D: 12.4 ± 1.8; p=0.016). The inflammatory cell numbers of irradiated samples were similar to controls (A: 65 ± 6; B:85 ± 9; C: 84 ±14, and D: 83 ± 3; p=0.443). The data showed that phototherapy with low intensity laser modulates the inflammatory reaction in the brain by increasing the cerebral vascular permeability after a cryogenic trauma.

This is a clinical presentation demonstrating the efficacy of laser therapy in the treatment of patients
presenting with trauma to both the hard and soft tissue in the orofacial region. The use of laser therapy aids
the management of these cases where the patients often present with anxiety and a low pain threshold. The
outcomes in these cases indicate good patient acceptance of the treatment, enhanced repair and tissue
response suggesting that this form of treatment can be indicated for these patients. A combination of hard
and soft lasers are used for the comprehensive dental management and treatment of these cases. The lasers
used are a 810nm diode and an Er.CrYSGG.

Low levels of light have been reported to change human physiologic activities. In our research we focused at an extreme
situation and utilized human's own ultra-weak light for radiation. Human photon emission was studied after dark-adaptation
utilizing a sensitive, cooled, moveable photomultiplier system. Data showed that palm and dorsum of the
hands showed most emission.
Human light was reflected by a red color filter in close proximity but not touching the body of the dark-adapted subject.
Photon emission from the palm was recorded before and after the filter was placed at 3 cm from the skin between the
palm and the photomultiplier. After removing the filter the photomultiplier recorded increased emission compared to
emission prior to exposure. The effect faded away in 7 min. To study whether this effect is only local, photon emission
of the hand dorsum was recorded and the filter was placed 3 cm below the palm. Such exposure also resulted in
increased emission that faded away. In this protocol, photon emission of the dorsum was also recorded during the period
that the palm was exposed to the filter. Photon emission increased immediately after positioning the filter.
As a first step to an explanation we discuss recent studies on the optical properties of human photon emission. The
photon signal has non-classical features and is well described by the photon signal in a coherent state. It is hypothesized
that the human photon field carries information on the chemical reactions in the physiologic state.

The advantages of the modified Nakatani method for diagnostics of energetic condition of meridians are described. Also
the perspectives of its clinical application for dynamic patient monitoring in treatment process are considered. The
model of a biological feedback through measurement of electric conductivity of a skin at pulse current is represented
with its mathematical and software base. The results of clinical tests of the treatment-and-diagnostic complex (TDC)
functioning in correspondence with the modified Nakatani method are analyzed.